The invention relates to a process for removing acid components or similar noxious materials from flue gases, preferably flue gases derived from coal or oil operated electric power stations where the flue gases prior to leaving the boiler apparatus are passed through an air preheater and are then subject to dust separation prior to treatment in a desulfurization apparatus.
A number of older power stations are still operating which do not have any desulfurization apparatus. The flue gases in these cases are simply passed through a dust separator before being discharged through the chimney. This kind of operation results in heavy air pollution.
In order to avoid this air pollution it has been proposed (German published and accepted application No. 27 53 902) to arrange a desulfurization apparatus prior to the dust remover and the discharged chimney. These desulfurization apparatus are known in many different forms. They are operated as wet or dry devices, see West German published application No. 27 25 892.
With these power stations which are provided with desulfurization devices, the problem is shifted from the air pollution to water and soil pollution. In a flue coal or oil operated energy process one has succeeded with substantial expense to considerably diminish both the air pollution and the soil pollution, see West German published application No. 23 24 547.
It has also become known from West German published application No. 19 61 048 to dry the flue gases in an injection evaporator which is operated with a suspension withdrawn from a then following wet washer. A useful dry end product cannot be obtained from these processes.
Industrial flue gases are apt to involve a multiplicity of noxious gaseous material, for instance HCL, HF, SO.sub.2, NO.sub.x, etc. As neutralizing agent all chemicals may be used normally which form solid salt materials with the noxious gas to be absorbed during a spray drying operation.
A particularly useful process for removing noxious gaseous material from flue gases has become known from the West German accepted and published application No. 24 31 130. The flue gases in this process are mixed in an injection evaporator with a salt solution which is obtained from the process itself and the mixture of flue gas and salt solution is then concentrated by evaporation. From the dry flue gases, dust particles and salt crystals are then almost completely separated as dry mixture. The glue gases with the acid components and the salt crystals which have not been separated out in the dust removal portion of the apparatus are circulated as part of an absorption fluid for absorbing the acid components and washing out and redissolving the remaining salt crystals. The evaporated water of the absorption liquid is replenished by fresh water. The salt solution is then withdrawn from this circuit and fed back into the injection evaporator.
The invention therefore has the object to provide for a process which permits the separation of noxious materials from flue gases with simple apparatus means and can be added to already existing power stations in an economical way, that is, may reduce the otherwise necessary apparatus investment.